Top 3 Point Guards:
1. Magic
2. Chris Paul
3. Steph Curry
(this one was tough... a lot of good point guards. I ultimately think Curry will be number 2. Guys like Stockton, Nash, Kidd, Thomas can probably be argued )
Personally, I don't discount Oscar Robertson that much, but I understand your reasoning for it. Of top PG's we have in no particular order there is Cousy, Oscar, Jerry West [who can be more argued as a combo guard I suppose], Isiah Thomas, John Stockton, Gary Payton, Jason Kidd, Steve Nash, Chris Paul, Russell Westbrook, Curry, and I'd say Lillard is entering the picture.
I can see your rationalization for including Chris Paul. I guess I just wouldn't, but you could make cases for a lot of these guys. I'd probably put Stockton and/or Gary Payton over Chris Paul. Of the list of available PGs here, Magic I think is pretty clear cut #1. After that it gets into a debate.
Top 3 Shooting Guards:
1. MJ
2. Kobe
3. Dwyane Wade
MJ is obviously going to be #1. And given the rest of the list of players available, you can really see the SG is something of a modern day creation versus past eras. Could say the same about PG's too. You got Kobe, Wade, Iverson, Drexler, Gervin, and probably Harden entering the picture and really that's it. I don't think by any means Drexler or Gervin are Top 3, so probably won't disagree with Kobe and Wade being there.
Top 3 Small Forwards:
1. LBJ
2. Bird
3. Durant
LBJ pretty indisputable as #1 there. This position gets a bit more interesting. But for a list of general SFs: Bird, Elgin Baylor, Rick Barry, John Havlicek, Julius Erving, Dominique Wilkins, Scottie Pippen, Kevin Durant.
Not sure I'd put Durant in this list yet when you have Julius Erving sitting nicely there as well. I think I'd put him there over Durant, could change in time though.
Top 3 Power Forwards:
1. Duncan
2. Karl Malone
3. KG
(Number 3 for me is tough. Guys like Dirk, KG, Barkley, and soon AD can all be argued. I just went with KG because he was so great all around... Great defender, passer, could shoot, post up... just everything.)
Not much to disagree on here as it's quite subjective. A lot of great players here that I don't feel entirely separate themselves out much over the others: Bob McAdoo, Elvin Hayes, Karl Malone, Charles Barkley, Tim Duncan, Kevin Garnett, Dirk Nowitzki, AD has potential to make this list, but dude, stop getting hurt lol.
Granted McAdoo and Hayes probably on a lower tier than the others. I think KG could be interchanged with several other guys on that list though. Duncan/Malone could be flip flopped if we're going off stats versus accomplishments.
Top 3 Centers:
1. Kareem
2. Shaq
3. Hakeem
The most crowded field in NBA history... Also probably quite debatable, though maybe as not as it would seem.
In the list of players: Wilt, Bellamy, Russell, Kareem, Unseld, Lanier, Cowens, Moses, Hakeem, DRob, Ewing, Shaq, Now I get why you're not willing to include Wilt and Bill Russell, and that's completely understandable. Kareem's longevity I think makes him a good case for #1. Shaq had more talent and just sheer ability to dominate for a long time. Hakeem put in the work and developed skills like no other center in my opinion. The rest of the centers, hard for me to put on the same tier as the others.